N(CF3)2 anion generation and its use

ABSTRACT

The invention relates to a process of generating N(CF 3 ) 2  anions by reacting a metal fluoride of formula MF x  with a compound of formula R F SO 2 N(CF 3 ) 2 , (CF 3 ) 2 N(SO 2 CF 2 ) m SO 2 N(CF 3 ) 2  or R F CON(CF 3 ) 2 . The invention further relates to the use of the N(CF 3 ) 2  anions as a reagent for the introduction of halogen or other organic groups into organic molecules.

This invention relates to a new process for the generation of N(CF₃)₂anions and their use for the introduction of N(CF₃)₂-groups into organicmolecules.

The chemistry of bis(trifluoromethyl)imido-anion is generally based onthe chemical transformation of perfluoro(2-azapropene), CF₃N═CF₂, as astarting material (H. G. Ang and Y. C. Syn, Advances in InorganicChemistry and Radiochemistry, Vol. 16 (1974), p. 1-64; A. Haas, GmelinHandbook of Inorganic Chemistry, 8th edition, Springer Verlag: BerlinHeidelberg New York (1981), Part 9, p. 125-153; A. Haas, Gmelin Handbookof Inorganic Chemistry, 8th edition, Springer-Verlag: Berlin -Heidelberg New York (1991), Suppl. Vol. 6, p. 196-214). This compoundcan be prepared in 78% yield by fluorination of CCl₃N═CCl₂ with excessof NaF in sulfolane at 105° C. (E. Klauke, H. Holtschmidt, K. Findeisen,Farbenfabriken Bayer A.-G., DE-A1-21 01 107 (1971/72) or by photolysisof CF₃N—(CF₂CFCl₂)Cl (Yield: 65-70%) (G. Sarwar, R. L. Kirchmeier and J.M. Shreeve, Inorg. Chem. 28 (1989, p. 2187-2189).Perfluoro(2-azapropene) is a gas at room temperature (B.p. −33° C.) andto make use of this compound a special equipment is required.

Very reactive di[bis(trifluoromethyl)imido]mercury, Hg[N(CF₃)₂]₂, wassynthesised at first by Young and co-workers (J. A. Young, S. N.Tsoukalas and R. D. Dresdner, J. Am. Chem. Soc. 80 (1958), p.3604-3606). This compound is a good reagent for the introduction ofN(CF₃)₂-groups into organic molecules (H. G. Ang and Y. C. Syn, Advancesin Inorg. Chem. and Radiochemistry, Vol. 16 (1974), p. 1-64; A. Haas,Gmelin Handbook of Inorganic Chemistry, 8th edition, Springer Verlag:Berlin Heidelberg New York (1981), Part 9, p. 45-46) but it is a notvery stable substance, which is extremely sensitive to the moisture. Thesynthesis of Hg[N(CF₃)₂]₂ is a hard and time-consuming work whichrequires special equipment and expensive starting materials.

Caesium bis(trifluoromethyl)imid, Cs⁺-⁻N(CF₃)₂, is another possiblecandidate for the synthesis of bis(trifluoromethyl)amino compounds. Thissalt can be prepared simply by bubbling of perfluoro(2-azapropene) intoa suspension of caesium fluoride in dry acetonitrile (A. F. Gontar, E.G. Bykovskaja and I. L. Knunyants, Izv. Akad. Nauk SSSR, Otd. Khim, Nauk(1975), p. 2279-2282).

 CF₃N═CF₂+CsF→Cs⁺ ⁻N(CF₃)₂

Disadvantage of this method is the formation of a dimeric product byreaction of the starting material perfluoro(2-azapropene) with cesiumsalt already formed:

CF₃N═CF₂+Cs⁺ ⁻N(CF₃)₂→CF₃—N═CF—N(CF₃)₂

This reaction seems to be nearly unavoidable and leads to the formationof a complex mixture of products.

Accordingly, there is a need for a new process for the generation ofN(CF₃)₂anions and their use for the introduction of N(CF₃)-groups intoorganic molecules. Especially, there is a need for such a new process,which does not need special security equipment, which may be handled insimple manner and avoids the building of undesired by-products at thesame time.

The problem is solved by a new process for the generation of N(CF₃)₂anions, which is characterised in that a sulphonamide of the generalformula

R_(F)SO₂N(CF₃)₂

wherein R_(F) means F or C_(n)F_(2n+1) and n is number between 1 and 4,is reacted with a metal fluoride of the general formula

MF_(x)

wherein M is Na, K, Rb, Cs, Ag, Cu or Hg with the proviso that x is 1 or2, if M means Na, K, Rb, Cs or Ag, and x=2 if M means Cu or Hg, formingan imino salt of the general formula

M^(x+)[⁻NCF₃)₂]_(x)

and the corresponding sulphonylfluoride of the general formula

R_(F)SO₂F

or

that a sulphondiamide of the formula

(CF₃)₂N(SO₂CF₂)_(m)SO₂N(CF₃)₂,

wherein m means 0 or 1, is reacted with a metal fluoride as mentionedabove forming an imino salt

M^(x+)[⁻N(CF₃)₂]_(x)

and the corresponding sulphonylfluoride

F(SO₂CF₂)_(m)SO₂F

or

that a N,N-Bis(trifluoromethyl)perfluoroacylamide of the general formula

R_(F)CON(CF₃)₂

is reacted with said metal fluoride forming said imino salt

and a salt of the general formula

R_(F)CF₂O⁻M⁺.

The process according to the invention takes place in an organic solventout of the group acetonitrile, ethylenglycoldimethylether and DMF ormixtures thereof. Preferably it is proceeded in acetonitrile, which isfree of water. According to the invention, the reaction may be proceededat a temperature between 15-100° C. Usually, good results are receivedat room temperature.

Suitable metal fluorides are fluorides of Na, K, Rb, Cs, Ag, Cu or Hg,but rubidium fluoride is the most preferred.

Advantageously, sulfonylfluorides, which are built as by-products duringthe reaction, may be collected, transformed again into starting materialand may be reused in the inventive process.

The imino salts of the general formula

M^(x+)[⁻N(CF₃)₂]_(x)

wherein M and x have the meaning given above, may be used as a reagentfor the substitution of halogen or other groups in organic molecules.Especially, [bis (trifluoromethyl)imido] rubidium,

Rb[N(CF₃)₂],

may be used as a reagent for the substitution of halogen or other groupsin organic molecules by a N(CF₃)₂-group.

Recently there has been developed a method for the synthesis of newN,N-bis(trifluoromethyl)perfluoroalkanesulfon-amides and -diamides (N.Ignat'ev, S. Datsenko, L. Yagupolskii, A. Dimitrov, W. Radek and St.Rudiger, J. Fluorine Chemistry (1995), 74, p. 181-186; P. Sartori, N.Ignat'ev and S. Datsenko, J. Fluorine Chemistry (1995), 75, p. 157-161;P. Sartori, N. Ignat'ev and S. Datsenko, J. Fluorine Chemistry (1995),75, p. 115-121).

These compounds can be prepared in a one-step procedure based on the useof simple starting materials, for example:

It has been found that sulphonamides (1), (2) and (3) are stablecolourless liquids, which are storable for a long time at roomtemperature (B.p. 30-31° C.; B.p. 56-57° C. and 85-86° C.,respectively). The handling of these compounds needs neither specialprecautions and nor a special equipment is required. Perfluorinatedsulphonamides like (1), (2) and (3) are nonhygroscopic substances, eventhey are not mixable with water, but they are fairly good soluble inorganic solvents, such as acetonitrile, ethylenglycoldimethylether, DMFand others, that provide handy conditions for the use of these compoundsin organic syntheses.

Now we have found by experiments that perfluorinated sulphonamides (1),(2) and (3) are suitable to react with metal fluorides forming thecorresponding sulfonylfluorides and imido salts (4) according to thefollowing general reaction:

Reaction (II):

x R_(F)SO₂N(CF₃)₂+MF_(x) →x R_(F)SO₂F+M⁺[⁻NCF₃)₂]_(x)  (4)

wherein

R_(F)=F or C_(n)F_(2n+1)

n=1-4

M=Na, K, Rb, Cs, Ag Cu, Hg and

x=1 or 2, with the proviso that x=1, if M has the meaning Na, K, Rb, Csor Ag, and that x=2, if M has the meaning Cu or Hg.

In special, we have found that (CF₃)₂N(SO₂CF₂)_(m)SO₂N (CF₃)₂ may reactwith a metal fluoride, preferably with an alkali fluoride, according tothe following general reaction:

Reaction (IIa):

(CF₃)₂N(SO₂CF₂)_(m)SO₂N(CF₃)₂+(3−x) MF_(x)→F(SO₂CF₂)_(m)SO₂F+(3−x)M⁺[⁻N(CF₃)₂]_(x)  (4)

wherein

m=0-1.

Rubidium fluoride is the mostly convenient reagent for the completetransformation of sulphonamides type (1)-(3) into imido salt (4).

The reaction may be proceeded at a temperature between 15-100° C.,preferably at room temperature, in a suitable organic solvent, which isfree of water. The solvent may be chosen out of the group acetonitrile,ethylenglycoldimethylether and DMF, but other polar solvents are alsouseful.

The most suitable solvent is dry acetonitrile, in which the reactiontakes place within a few minutes and results in the formation ofrubidium bis(trifluoromethyl)imid. This is a stable salt in solution atroom temperature for a long time and may be used for the followingsynthesis without isolation.

We also have found that N,N-Bis(trifluoromethyl)perfluoroacylamides type(5) are further suitable starting materials for the generation of imidosalts (4). These compounds (5) react with metal fluorides according tothe following general equation:

Compounds of type (5) can be prepared by the electrochemicalfluorination of corresponding N,N-dimethylperfluoroacylamides as it isdescribed in: J. A. Young, T. C. Simons and F. W. Hoffmann, J. Am. Chem.Soc. (1956), 78, p. 5637-5639.

Perfluorinated sulphonylfluorides that are formed as a by-productaccording to reaction (II) are either a gas at room temperature or veryvolatile liquids. At room temperature some amounts of sulfonylfluoridesremain in the acetonitrile solution. This does not cause any problem forthe introduction of N(CF₃)₂ groups into organic and inorganic moleculesusing imido salts (4).

Sulfonylfluorides resulting from the process (II) preferably arecollected from the gaseous phase and may be used again for the followingtransformation into starting materials for the preparation ofsulphonamides of type (1)-(3) by electrochemical fluorination inanhydrous hydrogen fluoride (Simons process). This reaction is forexample according to the following equation:

Reaction (IV):

CF₃SO₂F+2 HN(CH₃)₂→CF₃SO₂N(CH₃)₂+(CH₃)₂NH₂ ⁺F⁻

In the combination with the following electrochemical fluorination(Reaction I) this method gives the possibility to transform N(CH₃)₂groups into N(CF₃)₂ groups and imido salts (4). Therefore, Reaction IVis based on a cheap and commercially available material: dimethylamine.

In summary, the imido salt (4) is a convenient reagent for theintroduction of N(CF₃)₂ groups into organic molecules. For example itsalkali salts, preferably the rubidium salt, react at mild conditionswith benzyl bromide or -chloride and ethyl bromoacetate to formsubstituted products bearing a N(CF₃)₂ group (see reaction (V). Ingeneral, these salts seem to be suitable reagents for the substitutionof halogen or other groups in organic molecules:

Reaction (V):

C₆H₅CH₂Br+Rb⁺ ⁻N(CF₃)₂→C₆H₅CH₂N(CF₃)₂+RbBr

Reaction (VI):

C₆H₅CH₂Cl+Rb⁺ ⁻N(CF₃)₂→C₆H₅CH₂N(CF₃)₂+RbCl

Reaction (VII):

 BrCH₂COOC₂H₅+Rb⁺ ⁻N(CF₃)₂→(CF₃)₂NCH₂COOC₂H₅+RbBr

These reactions are given to demonstrate the synthetic utilities ofbis(trifluoromethyl)imido salts (4), which can be easily obtained fromperfluorinated sulphonamides type (1)-(3) and acylamides type (5) andmetal fluorides.

EXAMPLE 1 Preparation of Bis(trifluoromethyl)imido-rubidium and-Potassium Salts from CF₃SO₂N(CF₃)₂

To 2.185 g (21 mmol) of RbF in 10 cm³ of dry CH₃CN which are placed in aglass flask equipped with a condenser 6.127 g (21 mmol) of CF₃SO₂N(CF₃)₂were added drop wise. The reaction mixture was stirred at roomtemperature till all RbF was dissolved (some minutes). The resultingmixture was examined by ¹⁹F NMR spectroscopy. The signal at −37.5 ppm(s)belongs to the Rb⁺ ⁻N(CF₃)₂ salt. This was confirmed by addition to thereaction mixture of an identical sample of the Rb⁺ ⁻N(CF₃)₂ salt, whichwas prepared by the known procedure [6] from RbF andperfluoro(2-azapropene) in acetonitrile solution.

The similar procedure was used for the preparation of Rb⁺ ⁻N(CF₃)₂ saltstarting with RbF and FSO₂N(CF₃)₂.

The acetonitrile solution of Rb⁺ ⁻N(CF₃)₂ salt, prepared in the waywhich is described above, is stable at room temperature in a closedflask for a long time and can be used for the following chemicalreactions without additional purification (see examples 8, 9).

The bis(trifluoromethyl)imido sodium, potassium and cesium salts can beprepared by the same procedure starting from NaF, KF and CsF,respectively and CF₃SO₂N(CF₃)₂ or FSO₂N(CF₃)₂, for example:

2.85 g (10 mmol) of CF₃SO₂N(CF₃)₂ were added to 0.58 g of KF suspendedin 5 cm³ of dry acetonitrile and the reaction mixture was stirred atroom temperature for 1 hour. Solution was examined by ¹⁹F NMRspectroscopy. The signal −39.7 ppm (s) belongs to the K⁺ ⁻N(CF₃)₂ salt.

Published value for Cs⁺ ⁻N(CF₃)₂ and K⁺ ⁻N(CF₃)₂ salts is −34.2 ppm(broad singlet) relatively to CF₃COOH (external standard) (A. F. Gontar,E. G, Bykowskaja and J. L. Knunyants, Izv. Akad. Nauk SSR, Otd. Khim.Nauk (1975), p. 2279-2282).

EXAMPLE 2 Preparation of Bis(trifluoromethyl)imido-rubidium Salt fromC₄F₉SO₂N(CF₃)₂

To 0.041 g (0.39 mmol) of RbF in 1 cm³ of dry CH₃CN which were placed ina glass flask 0.170 g (0.39 mmol) of C₄F₉SO₂N(CF₃)₂ were added. Thereaction mixture was stirred at room temperature till all RbF wasdissolved (some minutes). The resulting mixture was examined by ¹⁹FNMRspectroscopy. The signal at −37.8 ppm(s) belongs to the Rb⁺ ⁻N(CF₃)₂salt.

EXAMPLE 3 Preparation of Bis(trifluoromethyl)imido-rubidium Salt from(CF₃)NSO₂N(CF₃)₂

To 0.064 g (0.61 mmol) of RbF in 1.5 cm³ of dry CH₃CN which are placedin a glass flask 0.120 g (0.32 mmol) of C₄F₉SO₂N(CF₃)₂ were added. Thereaction mixture was stirred at room temperature till all RbF wasdissolved. The resulting mixture was examined by ¹⁹FNMR spectroscopy.The signal at −37.2 ppm(s) belongs to the Rb⁺ ⁻N(CF₃)₂ salt.

The same procedure can be used for the preparation ofbis(trifluoromethyl)imido-sodium, -potassium and -caesium salts.

EXAMPLE 4 Preparation of Bis(trifluoromethyl)imido-rubidium Salt fromC₃F₇CON(CF₃)₂

To 0.092 g (0.88 mmol) of RbF suspended in 1.5 cm³ of dry CH₃CN in aglass flask 0.160 g (0.45 mmol of C₃F₇CON(CF₃)₂ was added. The reactionmixture was stirred at room temperature till all RbF was dissolved(approximately 10 min.). The resulting mixture was examined by ¹⁹F NMRspectroscopy. The signal at −37.2 ppm(s) belongs to the Rb⁺ ⁻N(CF₃)₂salt and the signals at −29.0 ppm, −80.8 ppm, −122.3 ppm and −125.9 ppmreflect the presence of CF₃CF₂CF₂CF₂O⁻ anion in the reaction mixture.

After addition of BrCH₂COOC₂H₅ to the reaction mixture and heating at80° C. during one hour the formation of substituted product,(CF₃)₂NCH₂—COOC₂H₅ was fixed by ¹⁹F NMR spectroscopy and GC analyses. Bythe dilution of the reaction mixture with water (CF₃)₂NCH₂COOC₂H₅ wasisolated as a pure substance (for details see example 8).

EXAMPLE 5 Preparation of Bis(trifluoromethyl)imido-silver Salt fromCF₃SO₂N(CF₃)₂

To 0.080 g (0.63 mmol) of AgF in 1 cm³ of dry CH₃CN which were placed ina glass flask equipped with a condenser 0.180 g (0.63 mmol) ofCF₃SO₂N(CF₃)₂ were added. The reaction mixture was stirred at roomtemperature for two hours. The resulting mixture was examined by ¹⁹F NMRspectroscopy. The signal at −47.0 ppm(s) belongs to the Ag⁺ ⁻N(CF₃)₂salt. After addition of C₆H₅CH₂Br to the reaction mixture and heating at80° C. for 10 minutes the formation of substituted productC₆H₅CH₂N(CF₃)₂, was fixed by ¹⁹F NMR spectroscopy and GC analyses. Bydilution of the reaction mixture with water C₆H₅CH₂N(CF₃)₂ was isolatedas a pure substance (for details see example 9).

EXAMPLE 6 Preparation of Bis(trifluoromethyl)imido-mercury Salt fromCF₃SO₂N(CF₃)₂

The mixture of 0.17 g (0.54 mmol) of HgF₂, 0.32 g (1.1 mmol) ofCF₃SO₂N(CF₃)₂ and 2 cm³ of dry CH₃CN was heated for 10 hours at 85° C.in a PTFE FEP cylinder, which was placed inside of a stainless-steelautoclave. After cooling, the clear liquid was separated from thedeposit and examined by ¹⁹F NMR spectroscopy. The signal at −46.3 ppm(s)belongs to Hg[N(CF₃)₂]₂salt. Published value for Hg[N(CF₃)₂]₂ is −48.7ppm (broad singlet) (R. C. Dobbie and H. J. Emeleus, J. Chem. Soc.(1996) (1), p. 367-370).

EXAMPLE 7 Preparation of Bis(trifluoromethyl)imido-copper Salt fromCF₃SO₂N(CF₃)₂

The mixture of 0.11 g (1.1 mmol) of CuF₂, 0.98 g (3.4 mmol) ofCF₃SO₂N(CF₃)₂ and 1.5 cm³ of dry CH₃CN was heated for 10 hours at 80° C.in a PTFE FEP cylinder, which was placed inside of a stainless-steelautoclave. After cooling, the clear liquid was separated from thedeposit and heated up to 80° C. in an argon stream to remove allvolatile products. The residue was examined by ¹⁹F NMR spectroscopy. Thesignal at −55.8 ppm (broad singlet) belongs to the Cu[N(CF₃)₂]₂ salt.After addition of Rb⁺ ⁻N(CF₃)₂ salt to this solution in CH₃CN only oneaverage signal at −38.0 ppm (broad singlet) which belongs to the⁻N(CF₃)₂ anion was observed in the ¹⁹F NMR spectra.

Application of bis(trifluorormethyl)imido salts for introduction of theN(CF₃)₂ group into organic compounds:

EXAMPLE 8 Reaction of Bis(trifluoromethyl)imido-rubidium Salt with EthylBromoacetate

To the solution of Rb⁺ ⁻N(CF₃)₂ salt which was obtained from 2.185 g ofRbF and 6.127 g of CF₃SO₂N(CF₃)₂ in dry acetonitrile (see example 1)3.13 g (18.7 mmol) of BrCH₂COOC₂H₅ were added. The mixture was keptboiling during one hour and diluted with water. The water insolubleliquid material was collected, washed with water and dried with MgSO₄.After distillation 2.73 g of pure (CF₃)₂NCH₂COOC₂H₅ were obtained.

Yield: 61%, B.p. 127128 ′C. [6]. ¹⁹F NMR spectra: δ (CF₃)=57.0 ppm(s)[6]. ¹H NMR spectra: δ(CH₂)=4.3 ppm(s).

EXAMPLE 9 Reaction of Bis(trifluoromethyl)imido-rubidium Salt withBenzyl Bromide

To the solution of Rb⁺ ⁻N(CF₃)₂ salt (see example 1) which was obtainedfrom 0.882 g (8.44 mmol) of RbF and 2.5 g (8.77 mmol) of CF₃SO₂N(CF₃)₂in 7 cm³ of dry acetonitrile 1.27 g (7.4 mmol) of C₆H₅CH₂Br were added.The mixture was kept boiling during one hour and diluted with water. Thewater insoluble liquid material was extracted with diethylether (3×5cm³), washed with water and dried with MgSO₄. After distillation 1.35 gof pure C₆H₅CH₂N(CF₃)₂ were obtained.

Yield 75%, B.p. 151-152° C. ¹⁹F NMR spectra: δ (CF₃)=56.8 ppm(t),J_(H,F)=1.5 Hz. ¹H NMR spectra: δ (CH₂)=4.5 ppm (q).

Reaction of Rb⁺ ⁻N(CF₃)₂ salt with benzyl chloride was done in the sameway as described above, except that the reaction mixture was keptboiling for 10 hours.

What is claimed:
 1. A process for the generation of N(CF₃)₂ anionscomprising reacting a sulphonamide of formula R_(F)SO₂N(CF₃)₂ whereinR_(F)=F or C_(n)F_(2n+1), and n=1-4, with a metal fluoride of formulaMF_(x) wherein M=Na, K, Rb, Cs, Ag, Cu or Hg, and x=1 or 2, with theproviso that x=1, if M is Na, K, Rb, Cs or Ag, and that x=2, if M is Cuor Hg, forming an imino salt of formula M^(x+)[N(CF₃)₂]_(x) and thecorresponding sulphonylfluoride of formula R_(F)SO₂F or reacting asulphondiamide of formula (CF₃)₂N(SO₂CF₂)_(m)SO₂N(CF₃)₂ wherein m=0 or1, with a metal fluoride of formula MF_(x) forming an imino saltM^(x+)[N(CF₃)₂]_(x) and the corresponding sulphonyldifluoride of formulaF(SO₂CF₂)_(m) SO₂F or reacting aN,N-Bis(trifluoromethyl)perfluoroacylamide of formula R_(F)CON(CF₃)₂with a metal fluoride of formula MF_(x) forming an imino salt M^(x+)[N(CF₃)₂]_(x) and a salt of the formula R_(F)CF₂O⁻M⁺.
 2. Aprocess according to claim 1, wherein the reaction takes place in anorganic solvent.
 3. A process according to claim 1, wherein the reactiontakes place in acetonitrile.
 4. A process according to claim 1, whereinthe reaction takes place in an organic solvent, which is free of water.5. A process according to claim 1, wherein the reaction proceeds at atemperature of 15-100° C.
 6. A process according to claim 1, wherein thereaction proceeds at room temperature.
 7. A process according to claim1, wherein the metal fluoride is rubidium fluoride.
 8. A processaccording to claim 1, further comprising collecting and transforming thesulfonylfluoride into R_(F)SO₂N(CF₃)₂, (CF₃)₂N(SO₂CF₂)_(m)SO₂N(CF₃)₂ orR_(F)CON(CF₃)₂.
 9. A process according to claim 2, wherein the organicsolvent is acetonitrile, ethylenglycoldimethylether, DMF or a mixturethereof.
 10. A process according to claim 8, further comprisingrecycling the R_(F)SO₂N(CF₃)₂, (CF₃)₂N(SO₂CF₂)_(m)SO₂N(CF₃)₂ orR_(F)CON(CF₃)₂ into the process.
 11. A method of substituting a halogenor other group in an organic molecule comprising using as a reagent animino salt of the formula Ag⁺[N(CF₃)₂].
 12. A method of substituting ahalogen or other group in an organic molecule comprising using as areagent an imino salt of the formula Cu²⁺[N(CF₃)₂]₂.
 13. A method ofsubstituting a halogen or other group in an organic molecule comprisingusing as a reagent an imino salt of the formula M^(x+)[N(CF₃)₂]_(x)wherein M=Na, Rb, Ag, Cu or Hg, and x=1 or 2, with the proviso that x=1,if M is Na, Rb, or Ag, and that x=2, if M is Cu or Hg, wherein the iminosalt is prepared by a method according to claim
 1. 14. A method ofsubstituting a halogen or other group in an organic molecule comprisingusing as a reagent an imino salt of the formula M^(x+)[N(CF₃)₂]_(x)wherein M=Na, K, Cs, Rb, Ag, Cu or Hg, and x=1 or 2, with the provisothat x=1, if M is Na, Rb, K, CS or Ag, and that x=2, if M is Cu or Hg,wherein the imino salt is prepared by a method according to claim
 1. 15.A method according to claim 11, wherein the group substituted in theorganic molecule is a halogen.
 16. A method according to claim 12,wherein the group substituted in the organic molecule is a halogen. 17.A method according to claim 13, wherein the group substituted in theorganic molecule is a halogen.
 18. A method according to claim 14,wherein the group substituted in the organic molecule is a halogen.